1. Field of the Invention
This invention relates to a zoom lens for use, for example, in a single-lens reflex camera, an electronic still camera, a video camera or the like.
2. Related Background Art
Some of zoom lenses in which a lens unit having negative refractive power precedes have a relatively great angle of view. In order to obtain a great back focal length, this forward negative refractive power has the action of decrease the angle of view relative to a rearward lens unit and turning the correction of curvature of image field and Petzval sum to the negative, and is suitable for aberration correction of a wide angle of view. Therefore, a lens construction in which a lens unit of negative refractive power is disposed most adjacent to the object side is adopted as a lens for a wide angle of view.
In this case, however, negative distortion occurs due to the negative refractive power most adjacent to the object side, and the angle of view increases and the bad influence thereof appears more remarkably. Therefore, use is made of a technique of disposing a positive lens near a negative lens to thereby mitigate the turning of distortion to the negative and correct distortion. This technique is considerably effective for aberration correction, but the addition of the positive lens increases the number of lenses and increases the volume of the lens, and this has led to the problem that the construction of the lens becomes complicated and the manufacturing cost is increased. Also, in a super-wide angle zoom lens, the correction of distortion is still insufficient even with the above-described correcting method, and the designing thereof has been extremely difficult and it has been difficult to maintain a good imaging performance.